Problem: A sulfur deficiency is relatively rare and will manifest itself as all-over chlorosis (yellowing of leaves), usually starting with the newer leaves and at first may look like a nitrogen deficiency.
The parts underneath the leaves may take on a pinkish red or orange color. The buds on a flowering plant may start dying off. Unlike most other deficiencies that cause yellowing of the leaves, a sulfur deficiency will start at the back of the leaf and move it’s way forward as opposed to starting at the tips.
Solution: Check and correct your pH to make sure that your sulfur isn’t being locked out. Sulfur moves slowly through the plant so it may take a few days after you fix the problem before you start noticing an improvement in your plant.